Incorporation of risk and updating in inspection of fatigue-sensitive details of ship structures

Abstract

Fatigue cracks, as a structural deterioration mechanism, may lead to unanticipated out of serviceof naval ships. Consequently, risk assessment andeffective inspection planning of naval ships under fatigue damage are needed to achieve economic and sustainableperformance of these structures.This paper presents a probabilistic framework for fatigue risk assessment and updating through inspection events. The computation associated with fatigue damage is performed using fracture mechanics and uncertainties are considered within this process.Furthermore, a quantitative risk assessment model using rating functions is presented to identify inspection priority among multiple fatigue-sensitive details. Bayesian techniques are adopted for reliability and risk updating of bothinspected and uninspected fatigue-sensitive details at component and system levels. Additionally, correlation of fatigue damage among different critical details is considered and incorporated within risk assessment and updating.A number of analyses are performed to investigate the fatigueriskranking assessment and updating. Applications are presented on anexisting tanker with multiple fatigue-sensitive details.

Reliability-based inspection planning in view of both crack initiation and propagation

“…S-N model calculates fatigue damage based on Palmgren-Miner' rule together with S-N curves, while FM model predicts damage evolution in terms of crack propagation. Most of studies on inspection planning are based on FM model (Dong and Frangopol, 2016, Kim et al, 2013, Soliman et al, 2016, Lassen and Recho, 2013. The reason is that FM model predicts evolution history of crack size and shape, which is comparable with inspection results.…”

“…The PoD (also the cumulative probability function for variable ) is given by = ( ) = 1 − exp(− ⁄ ) (16) where is the mean detectable crack size. The values associated with CVI and MPI are 2mm and 0.89mm respectively (Dong and Frangopol, 2016). The PoDs for CVI and MPI is given by Figure 1.…”

“…The smallest crack sizes 1 and 2 that can be detected by CVI and MPI are treated as variables and follow exponential distributions. The mean values for 1 and 2 are 2mm and 0.89mm respectively (Dong and Frangopol, 2016). The statistics and distributions for all the variables are listed in Table 2.…”

Probabilistic investigations into the value of information: A comparison of condition-based and time-based maintenance strategies

“…Common practice is to assume that they are mutually independent, e.g., is fixed and is a variable. In a probabilistic analysis, is typically assumed to be lognormally distributed (Guedes Soares and Garbatov 1998, Dong and Frangopol 2016, Faber et al 2005, Lotsberg et al 2016).…”

“…Although periodic inspections are simple to implement, they may not be as economically-efficient as non-periodic inspections. Similar to periodic inspections, non-periodic inspections have been applied to maintenance of general deteriorating structural systems (Zhao et al 2010, Jiang 2010, ships (Guo et al 2012, Dong and Frangopol 2016, Yang and Frangopol 2018, offshore assets and installations (Faber, Straub, and Goyet 2003, Faber et al 2005, Straub and Faber 2006, etc. A more complete, yet costly, information collection approach, may be continuous health monitoring.…”